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Study Design: Retrospective cohort study., Objective: This study investigates the incidence of long-term dysphagia in cervical disc arthroplasty, and anterior cervical discectomy and fusion (ACDF) patients., Summary of Background Data: No long-term comparison of dysphagia between cervical arthroplasty and fusion patients has been published. Widely variable short-term postsurgical dysphagia rates have been reported., Materials and Methods: Cohorts for this study are patients with single-level cervical degenerative disc disease previously enrolled in a randomized clinical trial comparing cervical arthroplasty and ACDF. Subjective modified Bazaz Dysphagia Severity questionnaires were distributed to each patient at a minimum of 5 years postoperative for the long-term assessment. Dysphagia severity data were pooled to compare the rate of patients with dysphagia (grade>1) to asymptomatic (grade=1)., Results: In the arthroplasty cohort, 15 of 22 (68%) patients completed long-term swallowing questionnaires with no reports of dysphagia. Eighteen of 25 (72%) ACDF patients completed questionnaires, with 5 of 18 (28%) reporting dysphagia. This is a statistically significant difference (P=0.042) favoring lower rates of long-term dysphagia after cervical arthroplasty at an average interval of 7 years postoperative (range, 5.5-8.5 y). No significant difference between rates of self-reported short-term dysphagia was noted with 12% (3/25) and 9% (2/22) in the ACDF and arthroplasty groups, respectively (P=0.56). All short-term dysphagia cases in the arthroplasty cohort reported complete resolution of symptoms within 12 months postoperative. In the ACDF cohort, persistent symptoms at 7 years were noted in all responding patients. Three ACDF patients reported new late-onset, which was not noted in the arthroplasty cohort., Conclusions: To date, these findings represent the longest reported follow-up interval comparing rates of dysphagia between randomized cohorts of cervical arthroplasty and fusion patients. Our study suggests that cervical arthroplasty is less likely than ACDF to cause sustained long-term or late-presenting dysphagia.

Study Design: Prospective, randomized, single-center, clinical trial., Objective: To prospectively examine the 7- and 10-year outcomes of cervical arthroplasty to anterior cervical discectomy and fusion (ACDF)., Summary of Background Data: Degeneration of the cervical discs causing radiculopathy is a frequent source of surgical intervention, commonly treated with ACDF. Positive clinical outcomes are associated with arthrodesis techniques, yet there remains a long-term concern for adjacent segment change. Cervical disc arthroplasty has been designed to mitigate some of the challenges associated with arthrodesis whereas providing for a similar positive neurological outcome. As data has been collected from numerous prospective US FDA IDE trials, longer term outcomes regarding adjacent segment change may be examined., Methods: As part of an FDA IDE trial, a single center collected prospective outcomes data on 47 patients randomized in a 1:1 ratio to ACDF or arthroplasty., Results: Success of both surgical interventions remained high at the 10-year interval. Both arthrodesis and arthroplasty demonstrated statistically significant improvements in neck disability index, visual analog scale neck and arm pain scores at all intervals including 7- and 10-year periods. Arthroplasty demonstrated an advantage in comparison to arthrodesis as measured by final 10-year NDI score (8 vs. 16, P = 0.0485). Patients requiring reoperation were higher in number in the arthrodesis cohort (32%) in comparison with arthroplasty (9%) (P = 0.055)., Conclusion: At 7 and 10 years, cervical arthroplasty compares favorably with ACDF as defined by standard outcomes scores in a highly selected population with radiculopathy., Level of Evidence: 1.

Study Design: Systematic review and meta-analysis., Objective: To determine the kinematics of the adjacent segments and global cervical spine after cervical arthroplasty compared with anterior cervical discectomy and fusion (ACDF)., Summary of Background Data: Adjacent segment pathology after ACDF is a significant concern. Arthroplasty may decrease the risk of adjacent segment degeneration by maintaining normal spinal kinematics compared with fusion. However, the differences in the in vivo kinematics of the adjacent segments after cervical fusion versus arthroplasty have not been clearly established., Methods: A systematic literature review of studies comparing adjacent segment kinematic changes between fusion and arthroplasty was performed. We included randomized controlled trials and cohort studies that compared cervical arthroplasty with ACDF in adults with degenerative disease and reported on at least 1 outcome of interest. Meta-analysis was performed using a random-effects model where appropriate. The standardized mean difference of changes from baseline to follow-up between treatment groups was determined. Recommendations were made using Grades of Recommendation Assessment, Development, and Evaluation criteria., Results: We identified 12 studies, including 7 randomized controlled trials, 4 cohort studies, and 1 case-control study that evaluated kinematic measurements at the adjacent segments or the global cervical spine (C2-C7) after cervical arthroplasty compared with ACDF. We found no statistically significant differences between treatment groups in the change in range of motion (ROM) at the cranial or caudal adjacent segments from baseline to 2 years of follow-up. However, there was low evidence that the global cervical spine (C2-C7) had significantly greater change in ROM after arthroplasty compared with ACDF: patients had a greater angular ROM as measured up to 2 years after arthroplasty. We found no statistically significant differences between treatment groups in the change in the horizontal or vertical centers of rotation at the adjacent segments as measured up to 2 years after surgery. Regarding sagittal alignment, the cranial and caudal adjacent segments both became significantly more lordotic after arthroplasty compared with fusion at 1 to 2 years after surgery. However, there was no statistically significant difference between treatment groups in the change in global cervical sagittal alignment from baseline to 2 years. CONCLUSION.: There is no statistically or clinically significant difference in the adjacent segment ROM or centers of rotation after cervical arthroplasty compared with ACDF. However, the change in sagittal alignment at the cranial and caudal adjacent segments was significantly more lordotic after arthroplasty compared with fusion. In addition, although we found that there was no statistically significant difference between treatment groups in the change in global cervical (C2-C7) sagittal alignment, there was a significantly greater change in the angular ROM of the cervical spine at up to 2 years after arthroplasty than occurred after fusion., Consensus Statement: Patients can be advised that single-level arthroplasty and ACDF result in clinically similar kinematic changes at short-term follow-up. Strength of Statement: Strong.

Background: The published two-year results of the pivotal U.S. Food and Drug Administration investigational device exemption trial with the use of the Bryan cervical disc arthroplasty compared with anterior cervical discectomy with fusion for treating single-level degenerative cervical disc disease revealed a significantly superior overall success rate in the arthroplasty group. The purpose of this study was to evaluate the midterm safety and effectiveness of the Bryan disc as an alternative to arthrodesis following anterior cervical discectomy., Methods: A prospective, multicenter randomized clinical trial was undertaken for the treatment of persistent radiculopathy or myelopathy due to single-level cervical disc herniations or spondylosis. Patients were randomized to treatment with either the Bryan disc (the arthroplasty group; 242 patients) or anterior cervical discectomy and fusion (the fusion group; 221 patients). Patients completed preoperative and postoperative self-assessment forms at specified intervals and had radiographs made preoperatively, at six weeks, and at three, six, twelve, twenty-four, and forty-eight months after surgery. The primary outcome measure was overall success, a composite variable of safety and efficacy measures. Numerous secondary measures were assessed. The follow-up data for up to twenty-four months have been previously published. We report in the present study the forty-eight-month data collected on 181 patients who received the Bryan disc and 138 patients who underwent anterior cervical discectomy and fusion., Results: The study groups were demographically similar. Substantial reduction in Neck Disability Index scores occurred in both groups compared with preoperative values. The greater improvement in the Neck Disability Index score in the Bryan disc cohort persisted through the four-year follow-up period (p < 0.001). The four-year overall success rates were 85.1% and 72.5% for the arthroplasty and fusion groups, respectively (p = 0.004). The improvement in the arm pain score was substantial for both groups and significantly greater in the Bryan disc cohort (p = 0.028), and the neck pain scores showed persistently greater improvement in the Bryan disc group at forty-eight months of follow-up (p = 0.001). Short Form-36 physical component score improvement remained greater among the Bryan disc cohort (p = 0.007). The mean range of motion for the Bryan disc was 8.08° and 8.48° at twenty-four and forty-eight months, respectively. Total and serious adverse event rates were similar between the groups., Conclusions: The forty-eight-month follow-up data in the present report showed consistent, sustained significantly superior outcomes for cervical spine arthroplasty compared with cervical spine fusion. The arthroplasty cohort continued to show significantly greater improvements in Neck Disability Index, neck pain score, arm pain score, and Short Form-36 physical component score, as well as the primary outcome measure, overall success, at forty-eight months following surgery.

Background: Ossification of the anterior longitudinal ligament and the anulus adjacent to an anterior cervical arthrodesis has been termed adjacent-level ossification development. Initial studies suggested an association with the placement of plates <5 mm from an adjacent disc space. A follow-up study demonstrated that this ossification rarely occurs in association with arthrodeses without plate fixation. In the present study, our goal was to determine the incidence of adjacent-level ossification in patients who underwent cervical arthrodesis with plate fixation as compared with that in patients who underwent cervical arthroplasty., Methods: We performed a post hoc analysis of prospectively collected data. Radiographic data for all patients from a single site were used. All postoperative, two-year, and four-year follow-up lateral cervical spine radiographs were collected and formatted to occlude the surgical level, blinding the readers as to the procedure performed. Three independent blinded surgeons graded the cephalad adjacent level for the degree of ossification at each time point. The data were statistically analyzed for significant ossification grade differences between arthrodesis and arthroplasty., Results: A total of forty-six patients (twenty-one with a Bryan total disc arthroplasty and twenty-five with an arthrodesis) were included. Both cohorts were derived from previous participation in a Level-I multicenter prospective randomized controlled trial stratified by site. Ossification scores based on independent assessment by three readers at multiple follow-up times were used. The arthrodesis group had significantly higher ossification scores than the arthroplasty group at both the two-year (p = 0.003) and the four-year follow-up interval (p = 0.004). Both cohorts showed significant increases in ossification from the two-year follow-up to the latest follow-up (p = 0.001 for the anterior cervical arthrodesis group and p = 0.008 for the arthroplasty group)., Conclusions: Our data conclusively demonstrate that cervical intervertebral arthroplasty is associated with a significantly lower incidence of adjacent-level ossification than arthrodesis with plate fixation at both the two-year and the four-year follow-up. Arthroplasty has the advantage of not being associated with adjacent-level ossification, which may decrease cervical spine motion above and below the surgical level.

Study Design: Prospective, randomized, Food and Drug Administration Investigational Device Exemption trial from one study site., Objective: Examine the radiographic sagittal alignment of the Bryan cervical disc for one-level disease., Summary of Background Data: Prospective, randomized studies demonstrate Bryan arthroplasty provides statistically better functional outcomes than anterior cervical discectomy and fusion. Uncontrolled case reports describe kyphosis after disc replacement. No prospective study has critically assessed sagittal alignment after cervical arthroplasty., Methods: Forty-eight patients reviewed with a minimum follow-up of 2 years. Quantitative motion analysis determined the change in overall (C2-C7) and treatment-level sagittal alignment, disc space heights, and range of motion., Results: Preoperatively, overall sagittal alignment was equivalent in the two groups. At 24-month follow-up, overall lordosis for the cohorts was not statistically different from preoperative values for each group. In addition, overall lordosis was not significantly different at 24 months when comparing Bryan patients with the fusion patients. The average change in disc angle from preoperative to immediate postoperative at the treated level in the Bryan disc group was a nonsignificant increase in lordosis of 0.92°. The anterior disc height was the same at all time points, but the posterior disc height was slightly (0.7 mm) more in the Bryan than in the fusion patients (P = 0.04). The angular range of motion in the Bryan group was statistically equivalent at all time points. At the fused levels, average range of motion decreased from 6.4° to 0.9° at 24 months (P < 0.0001)., Conclusion: With the Bryan disc, there was an insignificant increase in lordosis of 0.9° at immediate postoperative time point. Overall cervical sagittal alignment is not different between the experimental and control populations. This prospective study does not demonstrate a clinically significant increase in segmental kyphosis after Bryan disc arthroplasty. Global cervical lordosis is statistically equivalent between arthroplasty and fusion groups at 2 years follow-up.

Study Design: Prospective, randomized, controlled. Level 1 evidence., Objective: To report functional outcomes at 48 months follow-up on prospectively randomized patients to either the Bryan cervical disc prosthesis or anterior cervical discectomy and fusion (ACDF) at a single site., Summary of Background Data: Surgical treatment of cervical disc pathology can involve discectomy and fusion (ACDF), the gold standard technique. The safety and effectiveness of this procedure has been established and demonstrated in the literature, however, limitations have evolved and alternatives such as disc replacement are being investigated. Intervertebral disc replacement is designed to preserve motion, both at affected and adjacent levels avoiding limitations of fusion such as adjacent level degeneration. New onset degenerative changes and possible recurring neurologic symptoms may be deferred or eliminated with cervical disc replacement. A recent multicenter trial with 24 months follow-up has shown the Bryan disc to compare favorably with ACDF. Continued follow-up is needed to further evaluate and compare functional outcomes in both these cohorts., Methods: A total of 47 patients were enrolled at our site as part of an ongoing multicenter prospectively randomized study investigating ACDF versus Bryan cervical disc prosthesis. Functional outcomes are now reported at 48 months follow-up for our cohort of participants. Neck disability index score (NDI), VAS neck and arm and SF-36 both physical and mental as well as complications and reoperations will be reported., Results: Functional outcome data collected at routine follow-up for 48-months has favorably demonstrated improved functional outcomes for NDI, neck/arm pain VAS scores, and the SF-36 physical/mental health component scores for the Bryan arthroplasty and ACDF cohorts. The NDI scores for the Bryan arthroplasty preoperatively was 51 and at 48 months 10. For ACDF preoperative NDI score was also 51 and at 48 months 16.7. At 48 months NDI success, measured by >or=15 points NDI improvement demonstrated a 93.3% success for Bryan arthroplasty and an 82.4% success for ACDF. VAS neck pain scores for the Bryan arthroplasty preoperatively was 76.2 and at 48 months was 13.6. VAS neck pain scores for ACDF preoperatively was 80.6 and at 48 months was 28.1. Arm Pain scores were also measured and for the Bryan arthroplasty preoperatively measured 78.8 and at 48 months 10.8. For ACDF arm pain scores preoperatively measured 77.1 and at 48 months 21.7. These outcomes have not been associated with any degradation of outcome measures from 2 to 4 years. During the 48 months of follow-up at our institution we also report 6 secondary surgeries in our control group (ACDF) and only 1 in our investigational group (Bryan). Of the 6 surgeries in the control group performed, 3 or 12% to date were for adjacent level degenerative disease and 1 or 4% for remote level degenerative disc disease. The remaining 2 surgeries were performed on the same patient for a pseudarthrosis. In the investigational group there was only 1 secondary surgery performed to date for adjacent level disease 5%., Conclusions: At 48 months, cervical arthroplasty with the Bryan cervical disc prosthesis continues to compare favorably to ACDF at our institution. There has been no degradation of functional outcomes from 24 to 48 months for NDI, VAS of neck and arm, and SF-36. There has been a lower incidence of secondary surgeries for the Bryan arthroplasty cohort to date.

Study Design: Kinematic study of a single site in an investigational device exemption trial., Objective: Evaluate the center of rotation (COR) after Bryan cervical arthroplasty and compare adjacent segment motion after cervical disk arthroplasty and fusion using validated radiographic analysis., Summary of Background Data: The goal of cervical arthroplasty is to reestablish spinal kinematics after anterior decompression. Excellent maintenance of range of motion has been reported for a variety of the prostheses; however, the manner the prostheses perform this task is different. A parameter that may be as important as range of motion is restoring the quality of motion. One of the important components is the COR that is easily studied biomechanically but has not been reported from in vivo studies. Furthermore, the effects on the quality of motion at adjacent levels have not been studied. The purpose of this study is to determine the quality of motion after Bryan cervical disk arthroplasty at the target level and the adjacent segments., Methods: The first 48 patients diagnosed with single level cervical disk degenerative disease and associated myelopathy or radiculopathy from a single institution enrolled in the Bryan disk investigational device exemption trial were selected for inclusion. Twenty-two investigational patients and 26 anterior cervical discectomy and fusion controls were evaluated radiographically preoperatively and 3, 6, 12, and 24 months postoperatively. These results were analyzed using Quantitative Motion Analysis software manufactured by Medical Metrics Inc. Kinematic parameters included translation, sagittal rotation, anterior/posterior disk height, and the calculation of the COR both in the sagittal and coronal planes., Results: At the arthroplasty level, the COR shifted more posterior (0.3 mm, 1% end plate width) and cephalad (4.9 mm, 20% end plate width) compared with the preoperative position, however, this change was not statistically significant (P=0.06). The variability of the COR, however, was less after arthroplasty compared with preoperative values. There was no significant difference in the short term between the adjacent levels after fusion compared with the prosthesis. At later time points (12 and 24 mo), however, the COR was significantly posterior at the level above arthroplasty compared with fusion (P<0.01). COR X was not significantly (P>0.3) different below fusions compared with arthroplasty. Sagittal rotation significantly increased at the level above for both the fusion and prosthesis groups. A trend was noted for increased translation (2.5% end plate width) at the level above a fusion compared with the Bryan disk at 24 months postoperatively, but this did not reach statistical significance., Conclusions: Sagittal rotation increases above the level of the arthroplasty and fusion. In the long term, the arthroplasty group had a more posterior COR at the level above, compared with the level above a fusion. Translation at the level above a fusion was slightly increased but not statistically compared with the level above the arthroplasty with similar amounts of sagittal rotation (flexion/extension). Although not reaching statistical significance, the COR seemed to shift more posterior and cephalad at the arthroplasty level with less variability compared with the preoperative position.

Study Design: Cohort comparison of results of meta-analysis., Objective: To compare improvement in SF-36 after cervical spine surgery to total hip and joint arthroplasty., Summary of Background Data: Health-related quality of life outcome instruments allow comparison of different diseases and change with various treatments. Total hip and knee arthroplasty are accepted procedures with excellent outcomes. It is unknown if treatment of cervical spine disease approaches those results., Methods: A meta-analysis of SF-36 outcomes of total hip and knee arthroplasty was performed and compared to results after cervical discectomy and arthroplasty or fusion. Pooled means and SD were calculated and compared among treatment groups using analysis of variance., Results: Eighteen studies reporting results in patients having total hip and knee arthroplasty and 2 randomized controlled studies of cervical disc arthroplasty were identified. The baseline physical function was worse in the joint arthroplasty patients and the mental health scores were worse in the cervical spine patients. The mean improvements in PCS for disc, fusion, total hip, and total knee arthroplasty were 14.2, 12.5, 12.2, and 9.6, respectively. The improvement in the physical component score (SF-36) was significantly greater in the cervical arthroplasty compared to the other 3 groups. Cervical fusion improvement was similar to total hip arthroplasty and both were greater than total knee arthroplasty. MCS domain improvement was significantly better in the cervical spine groups., Conclusion: The SF-36 results were surprising and showed equal or greater short-term improvement in cervical spine patient's pain and function than that observed after joint arthroplasty, although all groups had substantial improvement. Greater MCS improvement was likely caused by a ceiling effect as joint arthroplasty on average had normal scores at baseline.

Study Design: A prospective, randomized, multicenter study of surgical treatment of cervical disc disease., Objective: To assess the safety and efficacy of cervical disc arthroplasty using a new arthroplasty device at 24-months follow-up., Summary of Background Data: Cervical disc arthroplasty preserves motion in the cervical spine. It is an alternative to fusion after neurologic decompression, whereas anterior decompression and fusion provides a rigorous comparative benchmark of success., Methods: We conducted a randomized controlled multicenter clinical trial enrolling patients with cervical disc disease. Ultimately 242 received the investigational device (Bryan Cervical Disc), and 221 patients underwent a single-level anterior cervical discectomy and decompression and fusion as a control group. Patients completed clinical and radiographic follow-up examinations at regular intervals for 2 years after surgery., Results: Analysis of 12- and 24-month postoperative data showed improvement in all clinical outcome measures for both groups; however, 24 months after surgery, the investigational group patients treated with the artificial disc had a statistically greater improvement in the primary outcome variables: Neck disability index score (P = 0.025) and overall success (P = 0.010). With regard to implant- or implant/surgical-procedure-associated serious adverse events, the investigational group had a rate of 1.7% and the control group, 3.2%. There was no statistical difference between the 2 groups with regard to the rate of secondary surgical procedures performed subsequent to the index procedure. Patients who received the artificial cervical disc returned to work nearly 2 weeks earlier than the fusion patients (P = 0.015)., Conclusion: Two-year follow-up results indicate that cervical disc arthroplasty is a viable alternative to anterior cervical discectomy and fusion in patients with persistently symptomatic, single-level cervical disc disease.

Background: Although there have been case reports describing the use of cervical disc arthroplasty for the treatment of myelopathy, there is a concern that motion preservation may maintain microtrauma to the spinal cord, negatively affecting the clinical results. As we are not aware of any studies on the use of arthroplasty in this scenario, we performed a cross-sectional analysis of two large, prospective, randomized multicenter trials to evaluate the efficacy of cervical disc arthroplasty for the treatment of myelopathy., Methods: The patients in the current study were a cohort of patients who were enrolled in the United States Food and Drug Administration Investigational Device Exemption studies of the Prestige ST and Bryan disc replacements (Medtronic, Memphis, Tennessee). The inclusion criteria were myelopathy and spondylosis or disc herniation at a single level from C3 to C7. Clinical outcome measures were collected preoperatively and at six weeks, three months, six months, twelve months, and twenty-four months postoperatively., Results: A total of 199 patients were included in the present study; 106 patients (53%) underwent arthroplasty, whereas ninety-three (47%) underwent arthrodesis. The Neck Disability Index, Short Form-36 scores, and specific arm and neck pain scores improved significantly from baseline at all time points. Patients in all four groups had improvement in the postoperative neurological status and gait function; at twenty-four months after surgery, 90% (95% confidence interval, 77.8% to 96.6%) of the patients in the arthroplasty group and 81% (95% confidence interval, 64.9% to 92.0%) of those in the arthrodesis group had improvement in or maintenance of the neurological status in the Prestige ST trial and 90% (95% confidence interval, 75.8% to 97.1%) of the patients in the arthroplasty group and 77% (95% confidence interval, 57.7% to 90.1%) of those in the arthrodesis group had improvement in or maintenance of the neurological status in the Bryan trial., Conclusions: We found that patients in both the arthroplasty and arthrodesis groups had improvement following surgery; furthermore, improvement was similar between the groups, with no worsening of myelopathy in the arthroplasty group. While the findings at two years postoperatively suggest that arthroplasty is equivalent to arthrodesis for the treatment of cervical myelopathy for a single-level abnormality localized to the disc space, the present study did not evaluate the treatment of retrovertebral compression as occurs in association with ossification of the posterior longitudinal ligament, and we cannot comment upon the treatment of this condition.

Cervical disk arthroplasty, one of the emerging motion-sparing technologies, is currently undergoing evaluation in the United States as an alternative to arthrodesis for the treatment of cervical radiculopathy and myelopathy. With both arthrodesis and arthroplasty, the primary surgical goal is thorough decompression of neurocompressive pathology--directly by removal of osteophyte and disk and indirectly by disk distraction. There is, however, one principal difference between arthrodesis and arthroplasty. With a solid fusion, resorption of osteophytes (in accordance with Wolff's law) further enhances decompression. In contrast, osteophyte resorption will not occur with motion-preserving arthroplasty. There are many challenges when deciding between arthrodesis and arthroplasty. Prosthetic performance demands exacting implantation techniques to ensure correct placement, thus placing increasing demands on special instrumentation and surgical skills. It is also important to understand the tribology (the study of prosthetic lubrication, wear, and biologic effects) of disk arthroplasty and to be familiar with currently available information regarding kinematics, basic science, testing, and early clinical results.

Objectives: Surgical navigation systems have been increasingly studied and applied in the application of spinal instrumentation. Successful disk arthroplasty requires accurate midline and rotational positioning for optimal function and longevity. A surgical simulation study in human cadaver specimens was done to evaluate and compare the accuracy of standard fluoroscopy, computer-assisted fluoroscopic image guidance, and Iso-C3D image guidance in the placement of lumbar intervertebral disk replacements., Methods: Lumbar intervertebral disk prostheses were placed using three different image guidance techniques in three human cadaver spine specimens at multiple levels. Postinstrumentation accuracy was assessed with thin-cut computed tomography scans., Results: Intervertebral disk replacements placed using the StealthStation with Iso-C3D were more accurately centered than those placed using the StealthStation with FluoroNav and standard fluoroscopy. Intervertebral disk replacements placed with Iso-C3D and FluoroNav had improved rotational divergence compared with standard fluoroscopy. Iso-C3D and FluoroNav had a smaller interprocedure variance than standard fluoroscopy. These results did not approach statistical significance. Relative to both virtual and standard fluoroscopy, use of the StealthStation with Iso-C3D resulted in improved accuracy in centering the lumbar disk prosthesis in the coronal midline., Conclusions: The StealthStation with FluoroNav appears to be at least equivalent to standard fluoroscopy and may offer improved accuracy with rotational alignment while minimizing radiation exposure to the surgeon. Surgical guidance systems may offer improved accuracy and less interprocedure variation in the placement of intervertebral disk replacements than standard fluoroscopy. Further study regarding surgical navigation systems for intervertebral disk replacement is warranted.

Various total disc replacement (TDR) designs have been compared to anterior cervical discectomy and fusion (ACDF) with favorable short and long-term outcomes in FDA-approved investigational device exemption (IDE) trials. The unique design of M6-C, with a compressible viscoelastic nuclear core and an annular structure, has previously demonstrated favorable clinical outcomes through 24 months. To evaluate the long-term safety and effectiveness of the M6-C compressible artificial cervical disc and compare to ACDF at 5 years. Prospective, multicenter, concurrently and historically controlled, FDA-approved IDE clinical trial. Subjects with one-level symptomatic degenerative cervical radiculopathy were enrolled and received M6-C (n=160) or ACDF (n=189) treatment as part of the IDE study. Safety outcomes were evaluated at 5 years for all subjects. The primary effectiveness endpoint was available at 5 years for 113 M6-C subjects and 106 ACDF controls. The primary endpoint of this analysis was composite clinical success (CCS) at 60 months. Secondary endpoints were function and pain (neck disability index, VAS), physical quality of life (SF-36, SF-12), safety, neurologic, and radiographic assessments. Propensity score subclassification was used to control for selection bias and match baseline covariates of the control group to the M6-C subjects. Sixty-month CCS rates were estimated for each treatment group using a generalized linear model controlling for propensity score. At 5 years postoperatively, the M6-C treatment resulted in 82.3% CCS while the ACDF group showed 67.0% CCS (superiority p=.013). Secondary endpoints indicated that significantly more M6-C subjects achieved VAS neck and arm pain improvements and showed maintained or improved physical functioning on quality-of-life measures compared to baseline assessments. The M6-C group-maintained flexion-extension motion, with significantly greater increases from baseline disc height and disc angle than observed in the control group. The rates of M6-C subsequent surgical interventions (SSI; 3.1%) and definitely device- or procedure-related serious adverse events (SAE failure; 3.1%) were similar to ACDF rates (SSI=5.3%, SAE failure=4.8%; p>.05 for both). Subjects treated with the M6-C artificial disc demonstrated superior 5-year achievement of clinical success when compared to ACDF controls. In addition, significantly more subjects in the M6-C group showed improved pain and physical functioning scores than observed in ACDF subjects, with no difference in reoperation rates or safety outcomes. [ABSTRACT FROM AUTHOR]

The article discusses a study to compare the rates of adverse events associated with disc arthroplasty versus those of anterior cervical discectomy and arthrodesis with allograft and plate. All the patients were evaluated before and after the surgery. More cervical spine reoperations occurred in the fusion group. Only one spinal cord injury occurred in the arthrodesis group and no patients had deep infection or death related to either procedure.

Cervical myelopathy can be successfully treated by artificial disk replacement; however, it is extremely important to understand the appropriate indications. The suitable situation is quite narrow—a focal disc herniation without retrovertebral compression, without significant facet pathology, and without multilevel stenosis. It is critical to recognize the contraindications for cervical arthroplasty. The vast majority of patients with myelopathy are not candidates for cervical arthroplasty due to multilevel pathology or significant degeneration. [ABSTRACT FROM AUTHOR]

This article reviews the kinematics of disc arthroplasty and the different ways that current devices attempt to replicate normal segmental motion. All disc replacements are capable of rotation but not all are able to independently translate. It is “constraint” over the degree-of-freedom controlling independent translation of a prosthesis that dictates whether its center of rotation is fixed or can attempt to adjust to that of the implanted motion segment. Ball-and-socket-type articulations are constrained, while mobile core prostheses are unconstrained. The ideal kinematic type is yet to be determined and it may be that different circumstances will be best managed by different types of prostheses. [ABSTRACT FROM AUTHOR]

Cervical arthroplasty has undergone a rapid evolution since the development of the original Cummins device. The evolution of metal-on-metal implants has occurred in parallel with the development of novel bearing concepts incorporating metal alloys, polymers, and ceramics. The current “state of the data” is presented including clinical outcomes of recently developed devices. While the early data from clinical trials are encouraging, there remains a need to demonstrate the viability of such techniques in the long term. [ABSTRACT FROM AUTHOR]

Study Design. Prospective randomized controlled trial. Objective. Compare range of motion (ROM) and adjacent segment degeneration (ASD) following cervical disc arthroplasty (CDA) versus anterior cervical discectomy and fusion (ACDF) at 20-year follow-up. Summary of Background Data. Anterior cervical discectomy and fusion is the standard of treatment for single-level cervical disc degeneration causing radiculopathy. CDA is claimed to reduce shear strain, and adjacent-level ROM changes are hypothesized to hasten ASD with ACDF. Materials and Methods. This study collected data on 47 patients randomized to ACDF or CDA. Lateral cervical spine radiographs were evaluated preoperatively, postoperatively, and at 20 years for alignment, ROM, ASD, and heterotopic ossification. Results. Eighty-two percent (18/22) of CDA patients and 84% (21/25) of ACDF patients followed up at 20 years. At 20 years, total cervical (C2--C7) ROM was statistically different between the CDA and fusion groups (47.8° vs. 33.4°, P=0.005). Total cervical ROM was not significantly different between preoperative and 20-year periods following CDA (45.6° vs. 47.4°, P=0.772) or ACDF (40.6° vs.33.0°, P=0.192). Differences in postoperative and 20-year index-level ROM following CDA were not significant (10.1° vs. 10.2°, P=0.952). Final ASD grading was statistically lower following CDA versus ACDF at both adjacent levels (P<0.005). Twenty-year adjacent-level ossification development was increased following ACDF versus CDA (P<0.001). Polyethylene mean thickness decreased from 9.4 mm immediately postoperatively to 9.1 mm at 20-year follow up (P=0.013). Differences in adjacent-level ROM from preoperative to 20-year follow-up in both the ACDF and CDA groups did not meet statistical significance (P>0.05). Conclusions. Cervical disc arthroplasty maintains index-level and total cervical ROM with very long-term follow-up. Total cervical ROM was higher at 20 years in CDA relative to ACDF. CDA results in lower rates of ASD and adjacent-level ossification development than ACDF. [ABSTRACT FROM AUTHOR]

Background Context: Various designs of total disc replacement (TDR) devices have been compared to anterior cervical discectomy and fusion (ACDF) with favorable outcomes in FDA-approved investigational device exemption trials. The design of M6-C with a compressible viscoelastic nuclear core and an annular structure is substantially different than prior designs and has previously demonstrated favorable kinematics and clinical outcomes in small case series.Purpose: To evaluate the safety and effectiveness of the novel M6-C compressible artificial cervical disc compared with ACDF for subjects with single-level degenerative cervical radiculopathy.Study Design/setting: Prospective, multicenter, concurrently and historically controlled, FDA-approved investigational device exemption clinical trial.Patient Sample: Subjects with one-level symptomatic degenerative cervical radiculopathy were enrolled and assigned to receive M6-C or ACDF.Outcome Measures: Pain and function (Neck Disability Index, VAS), quality of life (SF-36), safety, neurologic, and radiographic assessments of motion (both flexion extension and lateral bending) were performed. The primary clinical endpoint was composite clinical success (CCS) at 24 months.Methods: Using propensity score subclassification to control for selection bias, 160 M6-C subjects were compared to a matched subset of 189 ACDF controls (46 concurrent and 143 historical controls).Results: Both ACDF and M6-C subjects reported significant improvements in patient-reported outcomes at all time points over baseline. Overall SF-36 Physical Component Score and neck and arm pain scores were significantly improved for M6-C as compared to ACDF treatment. CCS and mean Neck Disability Index improvements were similar between M6-C and ACDF. Correspondingly, there were significantly fewer subjects that utilized pain medication or opioids following M6-C treatment at 24 months relative to baseline. Range of motion was maintained in subjects treated with M6-C. Subsequent surgical interventions, dysphagia rates, and serious adverse events were comparable between groups.Conclusions: M6-C treatment demonstrated both safety and effectiveness for the treatment of degenerative cervical radiculopathy. Treatment with M6-C demonstrated noninferiority for the primary endpoint, indicating a similar ability to achieve CCS at 24 months. However, for the secondary endpoints, M6-C subjects demonstrated significantly improved pain and function compared to ACDF subjects, while maintaining range of motion, improving quality of life, and decreasing analgesic and opioid usage at 2 years postoperatively relative to baseline. [ABSTRACT FROM AUTHOR]

In this article, the author reflects on a research related to treatment of cervical radiculopathy by anterior cervical discectomy and fusion (ACDF). Topics discussed include frequent adjacent-level degeneration as compared to arthroplasty, satisfactory results shown for cervical arthroplasty in clinical trials, and cervical fusion expected to be supplanted by cervical radiculopathy.